1. Technical Field
The invention relates to the fabrication of nano-scale and micro-scale structures. In particular, the invention relates to molds used in imprinting lithography.
2. Description of Related Art
A consistent trend in semiconductor technology since its inception is toward smaller and smaller device dimensions and higher and higher device densities. As a result, an area of semiconductor technology that recently has seen explosive growth and generated considerable interest is nanotechnology. Nanotechnology is concerned with the fabrication and application of so-called nano-scale structures, structures having dimensions that are often 50 to 100 times smaller than conventional semiconductor structures. Nano-imprinting lithography is a technique used to fabricate nano-scale structures.
Nano-imprinting lithography uses a mold to imprint nano-scale structures on a substrate. A mold typically contains a plurality of protruding and/or recessed regions having nano-scale dimensions. Such a mold is fabricated using electron beam (e-beam) lithography or patterning and dry etching, typically reactive ion etching (RIE) to create a nano-scale pattern in the mold. However, e-beam lithography is slow and therefore of limited use in high throughput or production situations. Moreover, e-beam lithography has limited resolution in the nano-scale range. For example, a mask prepared using micro or nano-patterning techniques (e.g., optical lithography or e-beam writing) has some residual roughness along mask pattern edges. RIE etching through the mask introduces surface roughness in the sidewalls of the patterns of the mold that at least mimic and may further exacerbate the edge roughness of the mask pattern. As such, the mask used in RIE etching defines the sidewall roughness of the nano-patterns of a mold and such roughness remains rough at the micro-scale even with extreme precision writing. Further, the RIE process causes crystal degradation to the mold material.
While holding much promise, the practical use of such fabricated molds has been somewhat limited. In particular, the surface roughness of the mold contributes to undesirable roughness of the imprint patterns of the mold. Further, crystal damage to the mold caused by RIE processing contributes to low mold reliability and limited mold useful life in manufacturing of nano-scale structures. Moreover, the fabrication of the molds is time consuming. As such, the conventional mold can be costly to use.
Accordingly, it would be desirable to fabricate a mold with higher reliability, higher nano-scale resolution, longer useful life and less surface roughness to the mold patterns using potentially low-cost, fabrication techniques at higher throughput. Such a fabricated mold would solve a long-standing need in the area of nanotechnology.